The present invention relates to a semiconductor integrated circuit device (IC) and more particularly to a semiconductor integrated circuit device which has a built-in power supply voltage conversion circuit.
In a semiconductor integrated circuit device, especially in a MOS integrated circuit device, degradation in reliability of a MOSFET due to hot carriers is becoming of concern accompanying the progress in refinement of the device geometry. For an IC using a MOSFET having channel length smaller than 0.8 .mu.m, it has become necessary to suppress the generation of hot carriers by setting the operating voltage to be below 5 V. As a result, use is being made of an IC (referred to as LVIC hereinafter) in which its internal circuits are driven at 3.3 V by lowering an external voltage (5 V) using a power supply voltage conversion circuit (V.C.) inside the IC, by taking the interface with a system employing the IC into account.
In an LVIC a sufficient electrostatic withstand voltage cannot be achieved even if electrostatic breakdown preventive measures similar to those for an IC having no built-in V.C. are implemented. In particular, the electrostatic withstand voltage between an external power supply pin and an input or output pin is unsatisfactory.